RE: [ATM] 'Commercial' annealed, rather than 'fine' annealed

[Mark Cowan <toolontop@yahoo.com>]

Hi Mark:

The logic is sound, a couple of comments:

When Newport does precision annealing for me, I'm
paying for electricity for the ovens.  This is what
they say.  The time doesn't seem to matter much.

The point of getting Pyrex precision annealed is to
reduce one of the variables in the glass' response to
working as much as possible.  If they had a grade
beyond precision I'd probably go for that. ;)

It's not that expensive, an 8% charge on mid-size
pieces.  Again, it's the electricity.  Even as
insurance it's worthwhile.

Another post mentioned that Carl Zambuto is doing his
own annealing to control the quality, and Richard
related one of the Newport horror stories about a
large blank that came in not annealed at all. (?)  

Well, a pal of mine when he went to work for Carl told
me that they were going to do this because they
consistently had to reject pieces for poor annealing -
but they buy them from all the manufacturers (Newport
and United Lens, I think he mentioned GlassFab as
well) and there was nobody who did proper annealing
100% of the time.  Now it's been a few years so the
details may differ, but it definitely wasn't like
"Newport doesn't anneal properly and the others do" -
it was "We can't get properly annealed glass from
anybody all of the time."

This is why inspection is vital!  You could get large
sheets of Polaroid from the Edmund's surplus outlet
(Anchor Optical Surplus)though I don't see any now -
polarization.com offers 19" wide film for $15/foot
currently.  This and a diffuse light source will test
an infinite number of blanks.  If it's bad and shows
stress that you didn't order - send it back! 

Or you could build your own annealer and take in work.
 But read what Zambuto's written about their headaches
(some really crazy results) in doing this even as a
commercial operation (yahoo group).

Cheers,
Mark Cowan
Salem, OR USA

where the Venus transit will only be virtual

--- Mark Holm <mdholm@telerama.com> wrote:
> Here is a little bit of logic.
> 
> 1. High quality annealing is slow, and therefore
> expensive.
> 2. Amateurs make up a very small fraction of the
> customers of an outfit 
> like Newport.
> Newport wouldn't bother to offer the higher grades
> of annealing just to 
> satisfy the amateur market.  It just wouldn't pay.
><snip>


	
		
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